Show Global Maximum SQL Connections in Use

Luke Hebert

- 2 minutes read - 249 words

When you’re sizing a database server or troubleshooting intermittent “Too many connections” errors, you need to know how many simultaneous connections your MySQL instance has actually handled. The max_used_connections status variable gives you that number directly.

The Command

Run this as a user with PROCESS privilege (typically root or a DBA account):

SHOW GLOBAL STATUS LIKE 'max_used_connections';

Example output:

+----------------------+-------+
| Variable_name        | Value |
+----------------------+-------+
| Max_used_connections | 142   |
+----------------------+-------+

What the Number Means

  • Value: The highest number of concurrent client connections that have been active at any single moment since the server last started.
  • Scope: Global, not per-session. It resets to zero on a server restart.
  • Comparison: Compare this against your max_connections system variable (SHOW VARIABLES LIKE 'max_connections';) to see how close you are to the ceiling.

When to Check This

  • After a traffic spike or application deploy, to confirm you have headroom.
  • Before raising max_connections, to see whether the current limit is actually being hit.
  • During incident response for connection-pool exhaustion errors.
SHOW GLOBAL STATUS LIKE 'Threads_connected';
SHOW GLOBAL STATUS LIKE 'Threads_running';
SHOW VARIABLES LIKE 'max_connections';

Threads_connected tells you the current live count, while max_used_connections tells you the historical peak. Together they give a clear picture of whether your connection budget is adequate.

Note

If max_used_connections is consistently close to max_connections, consider increasing the limit, tuning your application’s connection pool, or adding a connection proxy like ProxySQL to reduce the number of direct connections to the server.